Validating the dynamic downscaling ability of WRF for East Asian summer climate

Abstract

To better understand the regional climate model (RCM) performance for East Asian summer climate and the influencing factors, this study evaluated the dynamic downscaling ability of the Weather Research Forecast (WRF) RCM. According to the comprehensive comparison studies on different physical processes and experimental settings, the optimal combination of WRF model setups can be obtained for East Asian precipitation and temperature simulations. Furthermore, based on the optimal combination, when compared with climate observations, WRF shows high ability to downscale NCEP DOE Reanalysis-2, which provided initial and lateral boundary conditions for the WRF, especially for the precipitation simulation due to the better simulated lowlevel water vapor flux. However, the strengthened Western North Pacific Subtropical High (WPSH) from WRF simulation results in the positive anomaly for summer rainfall.

Impacts of land surface model and land use data on WRF model simulations of rainfall and temperature over Lake Tana Basin, Ethiopia

“…Recently, Weather Research and Forecasting (WRF) model has been applied as an RCM for research and operational purposes in many parts of the world, for example in Africa (Diaz et al., 2015), Europe (Banks and Baldasano, 2016), North America (Burakowski et al., 2016), and Asia (Cannon et al., 2017). Previous studies showed that the performance of WRF model is influenced by the selection of physical parameter schemes including, microphysics (Gao et al., 2017), radiation (Mooney et al., 2016), planetary boundary layer (Kim et al., 2015), cumulus (Mugume et al., 2017), and land surface model (Jain et al., 2017). Other model input such as initial boundary condition (Yang and Duan, 2016), land use data (Cheng et al., 2013), and domain size and resolution (Zeyaeyan et al., 2017) also affect the performance of WRF model.…”

Diagnosing added value of convection-permitting regional models using precipitation event identification and tracking

“…Studies generally also agree that the microphysics scheme can impact precipitation (e.g. Jankov et al, 2005;Rajeevan et al, 2010;Bryan and Morrison, 2012;Awan et al, 2011;McMillen and Steenburgh, 2015;Gao et al, 2015;Pieri et al, 2015), though this conclusion is not universal . Other factors such as the planetary boundary layer and radiation schemes are of lesser importance (Xu and Small, 2002;Jankov et al, 2005;Awan et al, 2011;Gao et al, 2015).…”

“…Downscaling analyses do not routinely compare RCM output with that of the underlying LBC, but studies have long suggested that LBC precipitation biases are heritable. For example, Warner and Hsu (2000) and Yang and Wang (2012) showed that precipitation varies strongly with choice of LBC, and Gao et al (2015) showed RCM bias ∼80% that of the underlying LBC. However, recent work suggests that wet bias is not the only cause of problems with precipitation characteristics in RCMs: in RCM simulations driven by an GCM with nearly unbiased total precipitation, Chang et al (2016) found that RCM precipitation events were nevertheless substantially too large, with their excess size compenstated by too-low intensities.…”

Replies to the reviewers' comments

“…APHRO's daily gridded precipitation, presently the only long-term, continental-scale, high-resolution daily product, is constructed based on the data collected at 5000-12 000 stations, which represent 2.3-4.5 times the data made available through the stations used for generating global gridded data (i.e., CRU, GPCC, and UDEL) (Yatagai et al, 2012). Thus, the APHRO dataset would give more confidence in the robustness of the results in comparison with other global precipitation datasets and is therefore widely used for evaluating the performance of RCMs in East Asia (Gao et al, 2017;Lau et al, 2017;Um et al, 2017). In addition, the CRU and APHRO products are used instead of station data accessible from the China Meteorological Administration, owing to the study area including in the domain of East Asia, extending beyond the territory of China.…”